agenda-libre-ruby/app/admin/user.rb

ActiveAdmin.register User do
  index do
    column :login
    column :email
    column :firstname
    column :lastname
    column :current_sign_in_at
    column :last_sign_in_at
    column :sign_in_count
    actions
  end

  filter :login
  filter :email
  filter :firstname
  filter :lastname

  form do |f|
    f.inputs 'Admin Details' do
      f.input :login
      f.input :email
      f.input :firstname
      f.input :lastname
      f.input :password
      f.input :password_confirmation
    end
    f.actions
  end
  controller do
    def permitted_params
      params.permit admin_user: %i[login email firstname lastname password
                                   password_confirmation]
    end
  end
end